1. Field of the Invention
This invention generally relates to a force sensor for a bicycle. More specifically, the present invention relates to force sensor that mounts to an outer side of a bottom bracket of a bicycle that is used to calculate at least one of power applied to bicycle pedals and torque applied to a crank axle.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. Recently, bicycles have been provided with cycle computers to inform the rider of various traveling conditions of the bicycle.
Bicycles are sometimes equipped with a force sensor (e.g., a torque-detecting device) for detecting force acting on the bicycle crank axle. In U.S. Pat. No. 7,516,677, issued Apr. 14, 2009 (assigned to Shimano Inc.), a cylindrical torsion-detecting sleeve member (force sensor unit) is provided on a crank axle for detecting a torque applied to the crank axle. In this arrangement, the sensor(s) are mounted to the sleeve member and the sleeve member is installed within the bottom bracket tube. However, this arrangement is complex and requires complete disassembly of the front crank assembly in order to install the force sensor.
In EP 1,361,822, sensors are positioned between a radial inner surface of the bottom bracket tube and a radially extending outer surface of an annular member that surrounds one of the crank axle bearings. One of the problems with this arrangement is that the sensor is exposed on the radially extending outer surface of the annular member prior to installation and can be damaged during the process of installing the annular member to the bottom bracket tube.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved crank axle force sensor arrangement that can be easily installed to the bottom bracket tube of the bicycle. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.